Air pollution is the introduction of particulates, biological molecules, or other harmful materials into the atmosphere, possibly causing diseases or death to humans. In addition to the particulates being harmful to humans, the atmosphere also contains some particulates possibly causing allergies in some specific areas, such as pollen and salts.
Of all the different kinds of air pollutions, smog is the most difficult one to avoid. The smog indicates dust existing in the atmosphere. If a person inhales the smog, it may cause cardiopulmonary diseases. Furthermore, the smog may decrease the visibility of the surrounding environment, thereby increasing the possibility of causing traffic accidents.
To prevent humans from the particulates in the atmosphere, the simplest way is to wear a mask. However, a common mask is difficult to effectively avoid inhaling the particulates. Therefore, some manufacturers install a filter on the mask, yet the filter obstructs the respiration of user, thereby causing the user to feel uncomfortable.